U.S. patent number 7,749,256 [Application Number 11/099,007] was granted by the patent office on 2010-07-06 for ratcheting fixation plate.
This patent grant is currently assigned to Warsaw Orthopedic, Inc.. Invention is credited to Robert A. Farris, Jason M. May, Alexander R. Vaccaro.
United States Patent |
7,749,256 |
Farris , et al. |
July 6, 2010 |
Ratcheting fixation plate
Abstract
Devices and methods for spinal fixation employ at least first
and second plates that are configured to allow progressive sliding
advancement of the plate members toward one another and limit
movement of the plate members away from one another after
installation. A spring member associated with one bone plate may
engage toothed section(s) on the other bone plate. The bone plates
may each have arms that are spaced from one another and engaged by
corresponding arms on the other bone plate. There may be more than
two bone plates, with multiple restricted movement regions.
Inventors: |
Farris; Robert A. (Cordova,
TN), May; Jason M. (Memphis, TN), Vaccaro; Alexander
R. (Gladwyne, PA) |
Assignee: |
Warsaw Orthopedic, Inc.
(Warsaw, IN)
|
Family
ID: |
36638996 |
Appl.
No.: |
11/099,007 |
Filed: |
April 5, 2005 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20060235398 A1 |
Oct 19, 2006 |
|
Current U.S.
Class: |
606/282 |
Current CPC
Class: |
A61B
17/8009 (20130101); A61B 17/7059 (20130101) |
Current International
Class: |
A61B
17/80 (20060101) |
Field of
Search: |
;606/61,69,280,70,71,281-299 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Robert; Eduardo C
Assistant Examiner: George; Tara R
Claims
What is claimed is:
1. A bone plate device comprising: a first plate member adapted to
be secured to a bone; a second plate member adapted to be secured
to a bone and coupled to said first plate member; said first plate
member including a first base section and first and second arms
spaced from one another and extending from the first base section
towards the second plate, the first base section and the first and
second arms defining a first gap; said second plate member
including a second base section and third and fourth arms spaced
apart from one another and extending from the second base section
toward said first plate member, said third arm engaging said first
arm and said fourth arm engaging said second arm, the second base
section and the third and fourth arms defining a second gap; said
first plate member having first and second toothed sections thereon
disposed on opposite sides of a longitudinal axis of said bone
plate device, each of said toothed sections comprising a plurality
of teeth; a spring member engaging said second plate member and
displaceably engaging said first and second toothed sections; a
groove extending along said third arm, across said second base
section, and along said fourth arm; wherein said spring member is
disposed in said groove; wherein engagement of said spring member
and said toothed sections enables progressive sliding advancement
of said plate members toward one another and limits movement of
said plate members away from one another; the first and second gaps
together form a single visualization port that is adjustable in
size depending upon an amount of the sliding advancement of said
plate members.
2. The device of claim 1 wherein said spring member comprises a
generally U-shaped spring member abutting said first and second
plate members and distinct therefrom.
3. The device of claim 2 wherein said spring member comprises first
and second integral pawls for displaceable engagement said first
and second toothed sections, respectively.
4. The device of claim 3 wherein said first and second pawls point
in generally opposite directions and wherein said first and second
pawls are disposed on opposite sides of said axis of said bone
plate device.
5. The device of claim 1 wherein said first and second arms include
said first and second toothed sections thereon, respectively.
6. The device of claim 1 wherein said first plate member comprises
a first curved section; wherein said second plate member comprises
a second curved section; wherein said first and second curved
sections define outer ends of the visualization port through said
bone device when said first and second plates are disposed a
maximum amount toward one another, said visualization port having a
width in a direction generally transverse to a line connecting said
first and second curved surfaces that is approximately equal to a
distance between said first and second toothed sections.
7. The device of claim 1 further comprising at least a first
fastener securing said second plate member to the bone; wherein
said spring member restrains said first fastener against backing
out after said fastener is fully installed.
8. The device of claim 7 further comprising at least a second
fastener securing said second plate member to the bone; wherein
said spring member further restrains both said first and second
fasteners against backing out after said fasteners are fully
installed.
9. The device of claim 1 where said toothed sections comprise a
plurality of teeth having bases and a plurality of spaces between
the bases of said teeth.
10. The device of claim 1 further comprising: a third plate member
adapted to be secured to a bone and engaging at least one of said
first and second plate members; third and fourth toothed sections
spaced from one another and each comprising a plurality of teeth; a
second spring member displaceably engaging said third and fourth
toothed sections; wherein engagement of said second spring member
and said third and fourth toothed sections enables progressive
sliding advancement of said third plate member toward said one
plate member and limits movement of said third plate member away
from said one plate member.
11. The device of claim 10 wherein said third plate member is
disposed closer to said first plate member than said second plate
member.
12. The device of claim 1: wherein said first and second arms are
disposed on opposing sides of said axis; each of said first and
second arms having an associated centerline; wherein said first and
second toothed sections are disposed on inner surfaces, with
respect to said axis, of said first and second arms, respectively;
wherein said third arm extends farther inward toward said axis than
said first arm and extends farther outward away from said axis than
said centerline of said first arm.
13. The device of claim 1 wherein distal portions of said first arm
are substantially enclosed by said third arm.
14. The device of claim 1: further including said first and second
arms having said first and second toothed sections thereon,
respectively; said first and second arms spaced from one another
and disposed on opposing sides of said axis; first and second
centerlines associated with said first and second arms,
respectively, and spaced from each other a first distance;
including said third and fourth arms extending toward said first
plate member and disposed on opposing sides of said longitudinal
axis; third and fourth centerlines associated with said third and
fourth arms, respectively, and spaced from each other a second
distance; wherein said first and second distances are approximately
equal.
15. The device of claim 1: wherein said spring member comprises a
generally U-shaped spring member abutting said first and second
plate members and distinct therefrom; said spring member comprising
first and second integral pawls for displaceable engagement said
first and second toothed sections, respectively; wherein said first
and second arms are spaced from one another and disposed on
opposing sides of said axis; wherein said first and second toothed
sections are disposed on inner surfaces, with respect to said axis,
of said first and second arms, respectively; first and second
centerlines associated with said first and second arms,
respectively, and spaced from each other a first distance; wherein
said second plate member has the second base section extending
between said third and fourth arms, and a groove extending along
said third arm, across said second base section, and along said
fourth arm; wherein said spring member is disposed in said groove;
said third arm engaging said first arm and said fourth arm engaging
said second arm; third and fourth centerlines associated with said
third and fourth arms, respectively, and spaced from each other a
second distance; wherein said first and second distances are
approximately equal; wherein said third arm extends farther inward
toward said axis than said first arm and extends farther outward
away from said axis than said centerline of said first arm; wherein
distal portions of said first arm are substantially enclosed by
said third arm; further comprising at least a first fastener
securing said second plate member to the bone; wherein said spring
member restrains said first fastener against backing out after said
fastener is fully installed.
16. The device of claim 15 further comprising: a third plate member
adapted to be secured to a bone and coupled to said second member;
third and fourth toothed sections spaced from one another and each
comprising a plurality of teeth; a second spring member
displaceably engaging said third and fourth toothed sections;
wherein engagement of said second spring member and said third and
fourth toothed sections enables progressive sliding advancement of
said second and third plates toward one another and limits movement
of said second and third plates away from one another.
17. A bone plate device comprising: a first plate member adapted to
be secured to a bone and having first and second arms spaced from
one another and disposed on opposing sides of a longitudinal axis
of said bone plate device; each of said first and second arms
having an associated centerline; each said first and second arms
having an inner surface, with respect to said axis, having first
and second toothed sections thereon respectively, each of said
toothed sections comprising a plurality of teeth; a second plate
member adapted to be secured to a bone and coupled to said first
plate member; said second plate member having third and fourth arms
spaced from one another with a gap there between, the third and
fourth arms extending toward said first plate member; said third
arm engaging said first arm and said fourth arm engaging said
second arm; a generally U-shaped spring member abutting said first
and second plate members and distinct therefrom, said spring member
displaceably engaging said second plate member and said first and
second toothed sections; wherein said third arm extends inward
toward said axis farther than said first arm and extends farther
outward away from said axis than said centerline of said first arm;
wherein said toothed sections form a portion of a locking mechanism
that allows progressive sliding advancement of said plate members
toward one another and limits movement of said plate members away
from one another.
18. The device of claim 17 wherein said third arm extends at least
as far out from said axis as said first arm.
19. The device of claim 18 wherein distal portions of said first
arm are substantially enclosed by said third arm.
20. The device of claim 17 wherein said third arm has top, bottom,
outer, and inner surfaces circumferentially enclosing a distal
portion of said first arm.
21. The device of claim 20: wherein said fourth arm extends inward
toward said axis farther than said second arm and extends farther
outward away from said axis than said centerline of said second
arm; wherein said fourth arm has top, bottom, outer, and inner
surfaces circumferentially enclosing a distal portion of said
second arm.
22. The device of claim 17 wherein said second plate member has a
base section extending between said third and fourth arms; and
further comprising a groove extending along said third arm, across
said base section, and along said fourth arm; wherein said spring
member is disposed in said groove.
23. The device of claim 17 further comprising at least a first
fastener securing said second plate member to the bone; wherein
said spring member restrains said first fastener against backing
out after said fastener is fully installed.
24. The device of claim 23 further comprising at least a second
fastener securing said second plate member to the bone; wherein
said spring member further restrains both said first and second
fasteners against backing out after said fasteners are fully
installed.
25. The device of claim 17 where said toothed sections comprise a
plurality of teeth having bases and a plurality of spaces between
the bases of said teeth.
26. The device of claim 17: further comprising a third plate member
adapted to be secured to a bone and engaging one of said first and
second plate members; said third plate member having fifth and
sixth arms spaced from one another and disposed on opposing sides
of said axis of said bone plate device; each of said fifth and
sixth arms having an associated centerline; wherein said one plate
member further comprises seventh and eighth arms extending away
from said one plate member; said seventh arm engaging said fifth
arm and said eighth arm engaging said sixth arm; further comprising
third and fourth toothed sections forming a portion of a second
locking mechanism that allows progressive sliding advancement of
said third plate member toward said one plate member and limits
movement of said third plate member and said one plate member away
from one another.
27. The device of claim 26 wherein said third and fourth toothed
sections are disposed on said seventh and eighth arms,
respectively.
28. The device of claim 26 wherein said one plate member is said
second plate member.
29. The device of claim 26 wherein said one plate member is said
first plate member.
30. The device of claim 26 wherein said third and fourth toothed
sections are disposed on said fifth and sixth arms,
respectively.
31. The device of claim 17: wherein said third arm has top, bottom,
outer, and inner surfaces circumferentially enclosing a distal
portion of said first arm; wherein said fourth arm extends inward
toward said axis farther than said second arm and extends farther
outward away from said axis than said centerline of said second
arm; wherein said fourth arm has top, bottom, outer, and inner
surfaces circumferentially enclosing a distal portion of said
second arm; further comprising a generally U-shaped spring member
abutting said first and second plate members and distinct
therefrom, said spring member displaceably engaging said second
plate member and said first and second toothed sections; wherein
said spring member comprises first and second integral pawls for
displaceable engagement said first and second toothed sections,
respectively; wherein said second plate member has a base section
extending between said third and fourth arms; and further
comprising a groove extending along said third arm, across said
base section, and along said fourth arm; wherein said spring member
is disposed in said groove; further comprising at least a first
fastener securing said second plate member to the bone; wherein
said spring member restrains said first fastener against backing
out after said fastener is fully installed.
32. The device of claim 31: further comprising a third plate member
adapted to be secured to a bone and engaging one of said first and
second plate members; said third plate member having fifth and
sixth arms spaced from one another and disposed on opposing sides
of said axis of said bone plate device; each of said fifth and
sixth arms having an associated centerline; wherein said one plate
member further comprises seventh and eighth arms extending away
from said one plate member; said seventh arm engaging said fifth
arm and said eighth arm engaging said sixth arm; further comprising
third and fourth toothed sections forming a portion of a second
locking mechanism that allows progressive sliding advancement of
said third plate member toward said one plate member and limits
movement of said third plate member and said one plate member away
from one another.
33. A method of fixing two vertebrae together using a bone plate
device having at least two bone plate members, comprising: securing
a first plate member to a first vertebrae by inserting a first
fastener through an opening in the first plate member and into the
vertebrae; said first plate member having first and second arms
with toothed sections thereon disposed on opposite sides of a
longitudinal axis of said bone plate device, each of said toothed
sections comprising a plurality of teeth; securing a second plate
member adapted to a second vertebrae by inserting a second fastener
through an opening in the second plate member and into the
vertebrae, wherein said second plate member has third and fourth
arms, a base section extending therebetween, and a groove extending
along said third arm, across said base section, and along said
fourth arm; coupling said second plate member with said first plate
member so as to enable progressive sliding advancement of said
plate members toward one another and limit movement of said plate
members away from one another by displaceably engaging a spring
member with said first and second toothed sections while said
spring member engages said second plate member, wherein said spring
member engaging said second plate member comprises said spring
member being disposed in said groove; and progressively sliding the
plate members towards one another and reducing a size of a
visualization port formed by intersecting gaps between the opposing
arms of each of the first and second plate members.
34. The method of claim 33 wherein displaceably engaging said
spring member with said first and second toothed sections comprises
deflecting distal portions of a generally U-shaped spring member
that is distinct from said first and second plate members.
35. The device of claim 34 wherein said spring member comprises
first and second integral pawls; and wherein displaceably engaging
said spring member with said first and second toothed sections
comprises displaceably engaging first and second pawls of said
spring member with said first and second toothed sections,
respectively.
36. The method of claim 33 including restraining said first
fastener against backing out by said spring member.
37. The method of claim 33 wherein coupling said second plate
member with said first plate member so as to limit movement of said
plate members away from one another comprises disposing pawl
sections of said spring member in spaces disposed between the bases
of the teeth of said toothed sections.
38. The method of claim 33 further comprising: securing a third
plate member to a third vertebrae; engaging said third plate member
with one of said first and second plate members so as to enable
progressive sliding advancement of said third plate member toward
said one plate member and limit movement of said third plate member
away from said one plate member by displaceably engaging a second
spring member associated with either said third plate member or
said one plate member with third and fourth toothed sections
associated with the other of said third plate member and said one
plate member.
39. The method of claim 38 wherein said one plate member is said
first plate member.
40. The method of claim 38 wherein said one plate member is said
second plate member.
41. A method of fixing two vertebrae together using a bone plate
device having at least two bone plate members, comprising: securing
a first plate member to a first vertebra; said first plate member
having first and second arms extending outward from the first plate
member and disposed on opposite sides of a longitudinal axis of
said bone plate device with a first gap there between; each of said
first and second arms having an associated centerline; each said
first and second arms having an inner surface, with respect to said
axis, having first and second toothed sections thereon
respectively, each of said toothed sections comprising a plurality
of teeth; securing a second plate member adapted to a second
vertebra; said second plate member having third and fourth arms
extending outward from the second plate member and toward said
first plate member with a second gap there between; engaging said
first arm with said third arm such that said third arm extends
inward toward said axis farther than said first arm and extends
outward away from said axis farther than said centerline of said
first arm; engaging said second arm with said fourth arm; coupling
said second plate member with said first plate member so as to
enable progressive sliding advancement of said plate members toward
one another and limit movement of said plate members away from one
another via said toothed sections; and attaching the first and
second plate members to the first and second vertebrae,
respectively, and forming a window by adjoining the first and
second gaps; wherein said second plate member has a base section
extending between said third and fourth arms; and further
comprising disposing a spring member in a groove extending along
said third arm, across said base section, and along said fourth
arm; and further comprising thereafter engaging said toothed
sections with said spring member so as limit movement of said first
and second plate members away from one another.
42. The method of claim 41 wherein coupling said second plate
member with said first plate member comprises deflecting distal
portions of a generally U-shaped spring member that is distinct
from said first and second plate members to engage said toothed
sections.
43. The method of claim 41 wherein engaging said first arm with
said third arm such that said third arm extends inward toward said
axis farther than said first arm and extends farther outward away
from said axis than said centerline of said first arm comprises
engaging said first arm with said third arm such that said third
arm extends inward toward said axis farther than said first arm and
extends outward away from said axis farther said first arm where
the two overlap.
44. The method of claim 41 wherein engaging said first arm with
said third arm comprises substantially circumferentially enclosing
a distal portion of said first arm with said third arm.
45. The method of claim 41: wherein engaging said first arm with
said third arm comprises substantially circumferentially enclosing
a distal portion of said first arm with said third arm; and wherein
engaging said second arm with said fourth arm comprises
substantially circumferentially enclosing a distal portion of said
second arm with said fourth arm.
46. The method of claim 41 wherein securing said second plate
member to the second vertebrae comprises securing said second plate
member to the second vertebrae using at least a first fastener, and
further comprising thereafter restraining said first fastener
against backing out by said spring member.
47. The method of claim 46 wherein securing said second plate
member to the second vertebrae comprises securing said second plate
member to the second vertebrae using at least first and second
fasteners, and further comprising thereafter restraining said first
and second fasteners against backing out by said spring member.
48. The method of claim 41 wherein coupling said second plate
member with said first plate member comprises disposing pawl
sections of a spring member in spaces disposed between the bases of
the teeth of said toothed sections.
49. The method of claim 41 further comprising: securing a third
plate member to a third vertebrae; said third plate member having
fifth and sixth arms disposed on opposite sides of said
longitudinal axis; each of said fifth and sixth arms having an
associated centerline; engaging said fifth arm with a seventh arm
and engaging said sixth arm with an eighth arm, said seventh and
eighth arms associated with one of said first and second plate
members, so as to enable progressive sliding advancement of said
third plate member toward said one plate member and limit movement
of said third plate member away from said one plate member another
via said third and fourth toothed sections, said third and fourth
toothed sections comprising a plurality of teeth.
50. The method of claim 49 wherein said one plate member is said
second plate member.
51. The method of claim 50 wherein said second plate member
comprises said third and fourth toothed sections.
Description
BACKGROUND
Spinal plates have been developed for stabilization of various
portions of the spine after various surgical procedures,
particularly spinal fusion procedures. Conventional spinal fixation
plates typically take the form of a unitary plate with a pair of
bone screw openings at opposing ends. The plate is placed over an
excavated bone graft-receiving site in the vertebral column, in
which a bone graft is located for fusion to adjacent vertebrae, and
secured in place with bone screws. These prior art spinal fixation
plates fix the adjacent vertebrae on opposite sides of the bone
graft-receiving site a set distance relative to one another.
While the fixation plates discussed above are suitable for some
situations, they also pose some difficulty in practice due to their
lack of adjustability to a particular patient's needs. In
particular, such fixation plates have a predetermined length with a
predetermined spacing between the screw holes. As such, when a
fixation plate with a different spacing is required for a
particular patient, another fixation plate must be made available.
As the particular needs of a patient may not be known prior to
surgery, this necessarily means that multiple sizes of plates must
be kept in ready inventory. In response to this, some forms of
variable length fixation plates have been proposed, with varying
degrees of success. The variable length devices allow the surgeon
to adjust the length of the device during surgery, and then to fix
that length via suitable locking mechanisms. However, even with
variable length devices, the overall length of the device is fixed
during surgery and does not change post-operatively.
It has been recognized that it may be beneficial to subject the
bone graft to compression over time as the graft fuses to the
vertebrae. Use of the conventional fixed length or variable length
spinal plates discussed above generally precludes compression of
the bone graft beyond any initial compression achieved during the
surgical procedure. As such, there remains a need for additional
approaches to spinal fixation, advantageously approaches that allow
the bone graft to be progressively compressed between adjacent
vertebrae over time.
SUMMARY
The present invention is directed to various embodiments of a bone
fixation device and methods of use, typically for spinal fixation.
One specific embodiment employs at least first and second bone
plate members adapted to be secured to bone portions, such as
adjacent vertebrae. The bone plate members are configured to allow
progressive sliding advancement of the plate members toward one
another and limit movement of the plate members away from one
another after installation. For example, a spring member associated
with one bone plate members may engage toothed section(s) on the
other bone plate member. The spring member may be a generally
U-shaped spring member abutting the first and second plate members
and distinct therefrom. The bone plate members may each have arms
that are spaced from one another and engaged by corresponding arms
on the other bone plate member. The arms may engage in a
male/female relationship, and the distal portions of the male arms
may be substantially enclosed by the corresponding female arms. The
centerlines of the arms may be substantially aligned when joined.
There may be more than two bone plate members, with multiple
restricted movement regions. Various combinations of these aspects
may also be employed as is appropriate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows one embodiment of the present invention attached to a
cervical portion of a spinal column.
FIG. 2 shows one embodiment of the present invention attached to
thoracic and/or lumbar portion of a spinal column.
FIG. 3 shows an exploded view of a bone plate device according one
embodiment of the present invention.
FIG. 4 shows the bone plate device of FIG. 3 in a partially-engaged
configuration.
FIG. 5 shows one embodiment of a "female" bone plate portion.
FIG. 6 shows one embodiment of a "male" bone plate portion.
FIG. 7 shows one embodiment of a spring member.
FIG. 8 shows another embodiment of a spring member.
FIG. 9 shows yet another embodiment of a spring member.
FIG. 10 shows another bone plate device according to another
embodiment of the present invention, having guide rails and
slots.
FIG. 11 shows a close up of a toothed section according to one
embodiment of the present invention.
FIG. 12 shows an exploded view of one multi-level embodiment of the
bone plate device.
FIG. 13 shows an exploded view of another multi-level embodiment of
the bone plate device.
FIG. 14 shows the device of FIG. 13 in an assembled state.
FIG. 15 shows one embodiment of a "female" bone plate portion
suitable for use in the bone plate device embodiment of FIG.
13.
FIG. 16 shows an exploded view of yet another multi-level
embodiment of the bone plate device, displaying one approach to
reversing the male/female relationship with respect to the
embodiment of FIG. 12.
DETAILED DESCRIPTION
One embodiment of the present invention is directed to a bone plate
device for fixing vertebrae in the spinal column of a patient. One
embodiment the device, generally designated 30 in FIG. 1, includes
a male bone plate 40, a female plate 80, and a spring lock member
100. The male bone plate 40, disposed in the inferior position in
FIG. 1, includes a generally U-shaped body with two arms 60a, 60b
and an intervening base section 42. The base section 42 includes
two holes 44 for receiving anchoring bone screws 5, which may
advantageously be counter-sunk. In addition, the base section 42
may include a third hole 46 for securing a locking ring or other
device (not shown) that acts to retain the bone screws 5 in place
once they are fully installed. The base section 42 has top 40T and
bottom surfaces 40B, which may be flat or advantageously slightly
curved to match the orthodic curve of the installation site, as
desired. The arms 60a,60b extend from the base section 42 and may
advantageously be disposed symmetrically about a midline of bone
plate 40, which advantageously coincides with the longitudinal axis
32 of the overall bone plate device 30. In addition, arms 60a,60b
have conceptual centerlines 68a,68b that are spaced from each other
a distance D.sub.MC and advantageously run generally parallel to
longitudinal axis 32. With respect to the longitudinal axis 32, the
arms 60a,60b have respective inner surfaces 66 and outer surfaces
67. The inner surfaces 66 include respective sections 70a,70b
having a plurality of teeth 72 therein, sometimes referred to
herein as the toothed sections 70a,70b. The teeth 72 of the toothed
sections 70a,70b advantageously have a non-symmetric profile with a
generally flat proximal face 74 disposed generally perpendicular to
the longitudinal axis 32 and an outwardly angled distal face 75. As
can be seen, these toothed sections 70a,70b may be disposed
proximally from the distal end portions of the arms 60a,60b. The
arms 60a,60b may have variable thickness, such as being thicker in
a portion 62 proximal to the base section 42 and thinner in a
section 64 distal from the base section 42, with an optional
shoulder 63 formed at the change in thickness. The section of the
arms 60a,60b extending from proximate the toothed sections 70a,70b
distally to their tips advantageously has a uniform thickness. The
inside surfaces 66 of the arms are advantageously joined by a
curved portion 43 of the base section 42 corresponding to the
inside center of the overall U-shape.
The female bone plate 80, disposed in a superior position in FIG.
1, includes a generally U-shaped body with two arms 90a,90b and an
intervening base section 82. The base section 82 includes two holes
84 for receiving bone screws 5, which may advantageously be
counter-sunk. In addition, the base section 82 may include a third
hole 86 for securing a locking ring or other device (not shown)
that acts to retain the bone screws 5 in place once they are fully
installed. The base section 82 has planar top 80T and bottom
surfaces 80B, which may be flat or advantageously slightly curved
to match the orthodic curve of the installation site, as desired.
The arms 90a,90b extend from the base section 82 and may
advantageously be disposed symmetrically about a midline of the
superior bone plate 80, which advantageously coincides with
longitudinal axis 32 of the overall bone plate device 30. In
addition, arms 90a,90b have conceptual centerlines 98a,98b that are
spaced from each other a distance D.sub.FC and advantageously run
generally parallel to the longitudinal axis 32. Each arm 90a,90b
includes a bay 92 that is intended to receive the distal portion 64
of a corresponding arm 60a,60b of the male bone plate 40, and
therefore generally corresponds in cross-sectional shape thereto.
With respect to the longitudinal axis 32, the arms 90a,90b have
respective inner surfaces 90.sub.SI and outer surfaces 90.sub.SO.
In addition, the arms 90a,90b have respective top surfaces 90T and
bottom surfaces 90B, which advantageously continue the shape of top
and bottom surfaces 80T,80B of base section 82. A groove 94 may be
formed on the inner surfaces 90.sub.SI that extends along one arm
90a, across the distal curved surface 83 of the base section 82,
and along the other arm 90b. Near each end of the groove 94, a
small passage 93 connects the groove 94 to the corresponding bay
92. If desired, top surface 90T may include a notch 96 extending
outwardly from the longitudinal axis 32 a short distance, proximate
the terminal ends of the groove 94. The groove 94 is intended to
accept the spring lock member 100, as discussed further below.
Advantageously, the arms 90a,90b may have relatively uniform
thickness, such as a thickness corresponding to that of the base
section 82 of the superior bone plate 80. In addition, it should be
noted the inside surfaces 90.sub.SI of the arms 90a,90b are
advantageously spaced a distance apart of D.sub.SI, which is
smaller than distance D.sub.T separating the toothed sections
70a,70b of the inferior bone plate 40.
The spring lock member 100, or simply spring member, is
advantageously generally U-shaped, with respective pawl barbs
102a,102b extending outward from the longitudinal axis 32 on each
end of the U-shape. The material of the spring member 100 may taper
towards the distal portion of the U-shape if desired, for added
flexibility. Each pawl barb 102a ,102b , or simply pawl,
advantageously has non-symmetric profile with a generally flat
proximal face 104 extending generally perpendicular to the
longitudinal axis 32, and a sloped distal face 105 that is angled
outward and backward to the proximal side of the spring member
100.
The spring member 100 is mated to the female bone plate 80 by
inserting the spring member 100 in the groove 94, with the barbs
102a ,102b facing outward. The optional notches 96 proximate the
terminal portions of the groove 94 aid in seating the barbs 102a
,102b properly. It should be noted that the tips of the barbs 102a
,102b are intended to extend through the passages 93 and into the
corresponding bays 92. The inherent spring force of the spring
member 100 helps urge the barbs 102a ,102b into position. As such,
it may be advantageous for the spring member 100, when in a natural
unconstrained state, to have a slightly flatter U-shape, but be
required to assume a narrower U-shape by interaction with the
superior bone plate 80 (e.g., by being restrained by the groove
94).
With the spring member 100 in place, arms 60a,60b of the male bone
plate 40 are inserted into the bays 92 of arms 90a,90b of the
female bone plate 80. Advantageously, the two bone plates 40,80 are
somewhat loosely coupled at this point, such that they can be moved
both toward and away from each other. Such a condition may be
achieved, for example, by having the pawls 102a ,102b of the spring
member 100 bear against the inner surfaces 66 of the arms 60a,60b
distally from the toothed sections 70a,70b. For ease of reference,
this configuration may be referred to as the pre-installation
configuration. The bone plate device 30 may be shipped from the
manufacturer in this pre-installation configuration, or the bone
plate device 30 may be assembled to this configuration after
shipment, but prior to or during surgery.
In use, a surgical site is opened and prepared in any known
fashion. At an appropriate point in the procedure, such as shortly
after a bone graft implant is placed in position, the bone plate
device 30 is installed by securing the bone plates 40,80 to their
respective vertebrae V1,V2 using bone screws 5 and holes 44,84.
During installation, the length of the bone plate device 30 may be
adjusted by sliding the bone plates 40,80 relative to each other.
Advantageously, during installation, the bone plates 40,80 are
moved toward each other so that pawls 102a ,102b of the spring
member 100 engage some of the teeth 72 of the toothed sections
70a,70b , such as the distal most teeth 72. For ease of reference,
this configuration may be referred to as the partially-engaged
configuration. In this partially-engaged configuration, the bone
plates 40,80 have limited ability to move apart due to the
engagement of the pawls 102a ,102b and the toothed sections
70a,70b. However, the bone plates 40,80 may be moved closer
together in a progressive ratcheting fashion due to the interaction
of the angled faces 75,105 of the pawls 102a ,102b and the teeth
72. During this forward or closing movement, the end portions of
the spring member 100, proximate the pawls 102a ,102b , are
deflected inward toward the longitudinal axis 32 until the next
tooth 72 is passed, at which point the inherent spring force of the
spring member 100 urges the pawls 102a ,102b outward to "lock-in"
the incremental movement. Thus, the surgeon is able to adjust the
bone plate device 30 to the desired initial length prior to closing
the surgical site.
Post-operatively, the bone plate device 30 described above is able
to continue to shorten (i.e., the proximal portions 48,88 of the
bone plates 40,80 are allowed to move toward each other)
incrementally, but is limited in its ability to lengthen, thereby
helping to ensure proper compression of the bone graft. Of course,
as the bone plate device 30 continues to shorten, the bone plates
40,80 will at some point reach a point of maximum movement toward
each other. For example, the tips of arms 90a,90b may abut against
the shoulders 63 formed on arms 60a,60b where the arms 60a,60b
change thickness, thereby preventing further shortening of the bone
plate device 30. For ease of reference, this configuration may be
referred to as the fully-engaged configuration.
As can be seen in FIG. 3, with arms 60a,60b engaging arms 90a,90b ,
the "female" arms 90a,90b advantageously extend farther inward
toward the longitudinal axis 32 than the "male" arms 60a,60b , and
also advantageously extend farther outward away from the
longitudinal axis 32 than the centerlines 68a,68b of their
counterpart arm 60a,60b. In some embodiments, the arms 90a,90b may
advantageously extend at least as far outward as their counterpart
arm 60a,60b , and optionally farther outward. Indeed, in some
embodiments, the female arms 90a,90b may substantially
circumferentially enclose the distal portions 64 of the male arms
60a,60b. Further, it should be noted that in some embodiments the
distance D.sub.FC between the centerlines 98a,98b of arms 90a,90b
is advantageously approximately equal to distance D.sub.MC
associated with centerlines 68a,68b of arms 60a,60b. While not
required in all embodiments, the advantageous spacing and/or
general alignment of the arms 60a,60b ,90a,90b discussed above
allows the curved sections 43,83 of the bone plates 40,80 to help
define a generally oval visualization port 34 through the bone
plate device 30, thereby allowing the surgeon to easily view the
bone graft between the vertebrae V1,V2. Advantageously, this
visualization port 34 exists in the pre-installation,
partially-engaged, and fully-engaged configurations. The width
W.sub.O of the visualization port 34 in a direction generally
transverse to a theoretical line connecting the two curved surfaces
43,83, such as along the longitudinal axis 32, is advantageously
approximately equal to the distance D.sub.T between the toothed
sections 70a,70b in the same direction.
In some embodiments, the spring member 100 may have an additional
proximal portion that acts to retain the bone screws 5 in place
once they are fully installed. This additional portion may, if
desired, take the form of two curved fingers 108 that approximate a
split circle. The fingers 108 may sit in a suitable recess in the
proximal portion 82 of bone plate 80, and flex inwardly when the
bone screws 5 are installed, but spring back out to retain the bone
screws 5 with the bone plate 80 and help prevent backing out of the
bone screws 5 after they are fully installed. As such, it may be
advantageous for the bone screws 5 to include small circumferential
shoulders on their heads. Backing out refers to inadvertent removal
or significant loosening of the bone screws 5 while installed in
the patient; intentional loosening and/or removal of the bone
screws 5 by, e.g., a surgeon, is not considered backing out. In
other embodiments, the end portions of the spring member 100,
proximate the pawls 102a ,102b, may optionally include small
inwardly extending tabs 110 that may include small holes 112.
Pulling inward on such tabs 110, such as with appropriate retaining
ring pliers extending through the holes 112, disengages the pawls
102a ,102b in the event such is needed to intentionally spread
apart the bone plates 40,80. Alternatively, some embodiments allow
the pawls 102a ,102b to be disengaged by inserting a suitable tool
into notches 96 and/or passages 93. In still other embodiments, the
legs of the spring member 100 may include small outwardly
protruding bumps 114, disposed closer to the base of the U than the
pawls 102a ,102b , that help retain the spring member 100 with the
bone plate 80 by resting in corresponding depressions (not shown)
in the arms 90a,90b.
The interconnection between the bone plates 40,80 may, in some
embodiments, further include inter-engaging rails 65 and slots 95
that help guide the sliding movement of the bone plates 40,80. In
this vein, the distal portion 64 of arms 60a,60b of bone plate 40
may include rails 65 that extend generally parallel to axis 32, and
are advantageously located along centerlines 68a,68b. These rails
65 mate with corresponding slots 95 in the arms 90a,90b of bone
plate 80. Alternatively, the rail 65 and slot 95 positions may be
reversed.
The teeth 72 of the toothed sections 70a,70b discussed above have
been assumed to be regularly spaced and disposed essentially
contiguously, with the base 76 of one tooth 72 abutting the base 76
of the adjacent tooth 72. However, such an arrangement is not
required in all embodiments. In some embodiments, the teeth 72 may
be spaced apart some amount, so that a significant space 78 exists
between the bases 76 of adjacent teeth 72. See FIG. 11. When a pawl
102a ,102b of spring member 100 is disposed in this space 78, the
bone plates 40,80 may move relative to each other, both forward and
backward, some small limited amount. With such an arrangement,
small movements by the patient that might otherwise cause the bone
plate device 30 to ratchet to the next shorter increment are
allowed without causing such ratcheting. Such spaces 78 may be
limited to being not more the size of the base 76 of the teeth 72,
so that, in effect, the toothed section 70a,70b has the appearance
of every other tooth 72 being removed. Other tooth profiles and
tooth/teeth configurations are also possible, such staggering teeth
72 on the different toothed sections 70a,70b , curved profiles for
the teeth 72, and the like.
The discussion above has been in terms of a bone plate device 30
having two bone plates 40,80 for fixing two adjacent vertebrae
V1,V2. However, some embodiments of the bone plate device 30 may
have more bone plates for fixing together more than two vertebrae.
For example, the multi-level bone plate device 30' of FIGS. 12-14
has three bone plates for fixing three adjacent vertebrae V1,V2,V3.
Two of the bone plates, the upper and lower bone plates 80',80'',
may be as described above for bone plate 80. The other bone plate,
the center bone plate 120, may be somewhat similar to bone plate 40
described above, but with four arms 60', two on each end. Thus, the
center bone plate 120 of such an embodiment has four arms 60' with
four corresponding toothed sections 70', and two curved sections
43'. For such a bone plate 120, the terms "proximal" and "distal"
are with reference to the midline thereof perpendicular to the
longitudinal axis 32' of the overall bone plate device 30'. In
addition, such a device 30' may have two spring members 100'
similar to spring member 100 discussed above. For such a
configuration, the upper and lower bone plates 80',80'' move toward
the center bone plate 120 from generally opposite directions along
the longitudinal axis 32' of the bone plate device 30'. To use such
a multi-level device, the upper bone plate 80' is secured to an
upper vertebrae V1, the center bone plate 120 is secured to a
middle vertebrae V3, and the lower bone plate 80'' is secured to a
lower vertebrae V2. The installation and movement limiting action
of such a device 30' is substantially as described above.
It should be understood that the male/female relationship of the
embodiments discussed above may be reversed without departing from
the scope of the present invention. For example, another embodiment
of a multi-level bone plate device is shown in FIG. 16. This
multi-level embodiment of the bone plate device 30'' is similar to
that described immediately above, but with the male/female
relationship reversed for the connection between center bone plate
120' and lower bone plate 40'. Thus, the center bone plate 120',
has two male arms (like arms 60a,60b) extending toward upper bone
plate 80', and two female arm (like arms 90a,90b) extending toward
lower bone plate 40'.
The bone plates 40,40',80,80',80'', and spring members 100,100' may
be made from any material or materials, such as titanium,
poly-ether-ether-ketone (PEEK), or the like, compatible for use in
an animal body over significant periods of time. Bioabsorbable
and/or resorbable materials may alternatively used.
The various embodiments of the bone plate device 30,30',30'' may be
used in various locations in the animal body, including without
limitation anterior or lateral locations on the cervical, thoracic,
and lumbar portions of the spinal column.
Other embodiments of the present invention may be carried out in
other specific ways than those herein set forth without departing
from the scope and essential characteristics of the invention. The
terms "upper", "lower", "inner", "outer", and the like are terms to
describe the relative positioning of different elements, and are
used in a general sense. The present embodiments are, therefore, to
be considered in all respects as illustrative and not restrictive,
and all changes coming within the meaning and equivalency range of
the appended claims are intended to be embraced therein.
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